Potassium-supplying welding flux ingredient



United States Patent POTASSIUM-SUPPLYIN G WELDING FLUX INGREDIENT JohnW. Donahey, Paoli, Pa., assignor to Foote Mineral Company, Philadelphia,Pa., a corporation of Pennsylvania No Drawing. Application June 9, 1953,Serial No. 360,605

4 Claims. (Cl. 148-26) The present invention relates to a novelcomposition of matter particularly adapted for use as an ingredient in awelding flux composition; and, more particularly, the invention relatesto a novel potassium-containing composition in the form a a frittedglass which is particularly adapted for use as an ingredient in awelding flux composition coating on a welding electrode for supplyingpotassium as an arc-stabilizing agent. The invention also relates to anovel welding flux composition, particularly in the form of a coating ona welding electrode, comprising the said potassium-containingcomposition, and to a welding rod coated with such flux composition.

In the art of arc welding, it has long been known that potassium presentin the flux coating on the welding electrode is capable of exerting apronounced effect upon the stability of the are. It has, therefore,become common practice to include in the welding electrode flux coatinga compound or compounds of potassium. Of the common forms in which thepotassium is introduced into the coatings, potassium feldspar has beengenerally preferred because of its low cost and good chemical stability.However, the high silica and alumina content of this mineral precludesits use in many types of coating formulations, particularly in the basictype coatings which are predominantly lime and which do not form glassyslags. In such cases, potassium has been added as a soluble potassiumsilicate, or as the hydroxide or carbonate. In the latter two instances,the hydroxide or carbonate has usually been predissolved in solublepotassium or sodium silicate solution and the resulting solution addedto the coating composition mixture to act as a binder and extrusion aid.The amount of potassium that can be introduced in this manner is limiteddue to the fact that either compound, when dissolved in a solublesilicate, alters the viscosity and other physical characteristics of thesilicate solution, and thus imposes certain limitations on themanufacturing procedure.

Even when the manufacturing problems are successfully surmounted, thepresence of potassium silicate, potassium carbonate or potassiumhydroxide in a welding electrode coating has one very deleteriouseffect. These materials are all hygroscopic, and tend to absorb largequantities of moisture from the atmosphere into the coating. This effectis undesirable in any type coating, since the performance of the coatedelectrode will vary according to the moisture content and thusmanufacture of electrodes of consistent operating characteristics isvirtually impossible.

Moreover, in recent years a type of flux coated welding electrode knownas the low hydrogen electrode has come into considerable use. Thiselectrode is employed in applications where very high strength weldmetal is required, and its effectiveness depends, in part,

on a very low content of moisture in the flux coating in order to avoidhydrogen embrittlement of the weld metal. The use of potassium silicate,potassium carbonate or potassium hydroxide in flux coatings for lowhydrogen-type welding electrodes obviously causes ditticulty.

In an attempt to reduce moisture reabsorption, a material knowncommercially as potassium titanate has been employed to supply thepotassium in the electrode coating. This material, as commonly supplied,has the approximate molar composition K2O.5TiO2. Although this materialis less soluble in water than potassium silicate, potassium hydroxide orpotassium carbonate, and is somewhat less hygroscopic than thesecompounds, it still possesses sufiicient hygroscopicity and solubilityto give rise to difficulties as a welding electrode coating constituent.It has been found further that this material varies in behavior withage. The same lot of material will have different effects upon theviscosity and plasticizing properties of the soluble silicates oralginates employed as binders and extrusion aids, depending upon thelength of time the material has been stored, and upon the storageconditions. It is believed that potassium titanate forms potassiumhydroxide by reaction with the water absorbed by it. This in turn reactswith the soluble silicate or the alginate, causing chemical breakdownand loss of plasticizing and binding properties. In order to avoid thesemanufacturing difiiculties, it has normally been necessary to employfreshly prepared potassium titanate. Even so, when the potassiumtitanate is present in the welding electrode coating, it issufiicieintly hygroscopic to cause diificulty, particularly in the lowhydrogen type of electrode, due to moisture reabsorption.

It is the principal object of the present invention to provide apotassium-containing composition which is insoluble in water and whichis hydrophobic, that is to say, possesses no significant hygroscopicity,and which is otherwise highly suited for use as a constituent in weldingelectrode flux coatings.

It is a further object of the invention to provide apotassium-containing composition which is not only in soluble andnon-hygroscopic but which is also low in silica and alumina and which ishigh in its potassium content.

Other objects including the provision of an improved welding electrodeflux composition, particularly in the form of a coating on a weldingelectrode, and a flux coated welding electrode, which affords a highdegree of stabilization of the arc during welding without, however,presenting the difiiculties encountered when the usualpotassium-containing materials are employed as are stabilization agents,will become apparent from a consideration of the following specificationand claims.

The novel potassium-containing composition of the present invention is awater-insoluble, non-hygroscopic glass in the form of a frit having ananalysis comprising between about 20% and about 33% of K20; betweenabout 20% and about 40% of TiOz, and between about 17% and about 40% ofSiOz, the sum of the K20 and TiO2 and SiOz making up between about andabout 94% of the glass; at least one divalent oxide selected from thegroup consisting of CaO (in an amount between about .5 and about 10%),MgO (in an amount between about .1 and about 8%) and MnO (in an amountbetween about .5 and about 15 and at least one of the trivalent oxidesselected from the group consisting of F6203 (in an amount between about.1 and about 15%), B203 (in an amount between about .5 and about 20%),and, A1203 (in an amount between about .1 and about 8%). The glass willcontain no more than about 5% of other oxides such as CrzOs, NiO, W03,MoOa, V205, CeOz, and the like. In other words, the K20, TiOz, SiOz,divalent oxide and trivalent oxide will make up at least about 95% ofthe glass.

The preferred glass frit of the present invention will comprise betweenabout 24% and about 29% of K20; between about 22% and about 33% of TiOz,and between about 24% and about.32% of SiOz, thesum of the K20 and TiOzand SiOz making up between about 78% and about 90% of the glass; atleast one of the divalent oxides selected from the group consisting ofCaO (in an amount. between about 1 and about 6%), MgO (inanamountbetweenabout l and about 3%) and MnO (in anamount betweenabouti3 and about and at least one of the trivalent oxides selected fromthe group consisting of. FezOa- (in an amount between about 4% and about10%), B20a- (inan amount between about. 1% and aboutv 10% and A1203 (inan amount between about 2% and about 5%). In this preferred glass of theinvention, there willbe no more than about 3% of other oxides, such asCrzOs, NiO, W03, M003, V205, CeOz,.and the. like. Inother words, theK20, TiOz, SiOz, divalent oxide and trivalent oxide will make up atleast about 98% of the glass. The percentages referred to in this andthe preceding paragraph are percentages by. weight.

It will be notedfrom' the foregoing that the content of potassium in theglass fritis relatively high as compared to, certainv of thepotassium-supplying materials previously used, e. g. potassium feldspar,so that smaller quantities of the composition are required to provide agiven potassium content in the coating. Furtherv in this connection, itwill be noted that the content of silica and: ofalumina: is. relativelylow and. this is tobe contrasted to potassium feldspar wherein the acidoxides,

i. e. alumina and silica, are unfavorably high. In view of thematerialsmaking up the glass, itwas wholly unexpected that a glass could even beformed containing as little as 40% Si02,. much less silica contentsbelow 40% and as. low as about It will also be noted that the glasscontains a substantial amount of TiOz. As is known in ceramic practice,TiOz is an: excellent opacifier, and numerous enamel compositions arebased on the recrystallization of TiOz. from the moltenvitreous enamel.This recrystallization is based on the very low solubility of TiOz-ofmost glass. compositions. It is most unexpected; therefore,-that theglasses of. the present invention are completely homogeneous. Finally,glasses of the present invention are insoluble in water and momhygroscopic. Glasseshigh in-KzO are notoriously. soluble, and, aspointed out above, many potassium compounds are relatively hygroscopic;The unusual insolubility and non-hygroscopic properties of the glassesof the present invention are, therefore, wholly unexpected; This.combination of high potassium content, low silica content, insolubilityand non-hygroscopicity in a homogeneous glass frit, therefore,provides-a material which; is. ideally adapted for inclusion in awelding'electrode flux coating to supply'potassium for arestabilization.

As stated, the glass composition of the present invention is in the.form of a frit in relatively fine particle size for ready incorporationwith the other flux ingredients and application to the welding rod. Theglass frit may be prepared in accordance with conventional frit-makingpractice. As is Well known, in preparing a frit, materials providingultimately the desired analysis-in the present case materialsprovidingthe above set forth oxide analysis-are mixed together: and melted. Withrespect to the materials employed toprovide the desired coniposition,such materials maybe selected from a wide range of well known; compoundsand minerals, and'the provision of the above-described oxide analysiswill present no problemsto those skilled in the art; Thus, the K20 maybeprovided by potassium. carbonate, potassium nitrate, potassiumhydroxide, and the. like; the TiOzmay be provided by, rutile, titanite,ilmenite,.titani: ferous slags, titanates, and the like. TheSiOz may beused as such or it may be providedby. othencompounds and minerals suchas silicates. The divalent and trivalent oxides may be used as such ormay be provided by other compounds. For example, such oxides may bepresent in certain of the minerals used to provide the other oxides ofthe formula. During melting, of course, volatile constituents will beliberated and driven off. For example, where carbonates are employed,carbon dioxide will be driven ofi.

The materials providing the desired chemical analysis within the rangesset forth above upon melting thereof, are mixed together in accordancewith common practice The resulting frit may be too coarse for directuse,

and may, therefore, require grinding. The grinding may be carried out inconventional grinding apparatus, for

example, in a jar mill, (a small sized, pebble mill com-- prising avitreous porcelain jar and gasketed porcelain.

lid and generally charged with porcelain balls or flint pebbles) rodmill, or the like. coarse frit to the desired fine particle size.Generally,

the particle size of the ground frit will be less thauabout 4O mesh-.andmay be as fine as 325 mesh or finer.

In preparing a flux coating comprising the novel glass frit of thepresent invention, a minor proportion of the glass frit is mixed withthe desired welding flux ingredients and a suitable binder. The specificwelding flux ingredients employed, as is well known, may be selectedfrom a wide variety of materials dependingv upon many factors, includingthe type of weld metal, the typeof metal being welded, the conditions ofwelding, certain properties desired in the coating, e. g. whether itwill provide a shielded are or not, and the like. Thetypesandcombinations of fluxingredients with whichthe. present glass frit isincorporated, are immaterial from the standpoint of the presentinvention.

In general, welding flux ingredients are inorganic substances which arerelatively stable at temperatures below about 1250 F. and which arerelatively insoluble in water. By way of illustration, the followingflux ingredients are given: carbonates (especially for use in.

shielded-arc flux coatings), such as calcium carbonate, magnesiumcarbonate, dolomite, lithium carbonate, and the like; fluorides, such ascalcium fluoride, sodium. fluoride, lithium fluoride, cryolite,fluorspar, and the like; oxides, such asiron oxide (e; g. hematiteand/ormagnetite), manganese oxide [e. g. manganese ore,hausmannitetMnsOt) and/ or mangenous oxide], silicon dioxide, titaniumdioxide (e. g. rutile and/orilmenite), zirconium dioxide, nickel oxide,columbium oxide, and the like;,silicates, such as aluminum silicate (e.g. glass, mica, feldspar, pyrophyllite, lepidolite, spodumene, etc),calcium silicate (e. g. wollastonite), magnesium silicate (e. g.-asbestos, talc, etc.), and the like; titanates; metallics for alloyingwith the weld metal, such as ferromanganese, ferrosilicon,ferrotitanium, ferrochromium,

ferrozirconium, ferrovandium, ferrocolumbium, iron,.silicon, manganese,tungsten, molybdenum, and the like.

With respect to the binder employed, it may be, in accordance with thebroader aspects of the present in-- vention, any of the bindingmaterials conventionallyemployed inthe preparation of flux coatings,such as thesoluble sodium or potassium silicates, gums, e. g. alginates,and the like. A particularly advantageous binding material, however, is.that disclosed in copending application Ser. No. 241,900, filed August14, 1951,, In accordance with; -said..copending application, there isemployed a low melting, hydrophobic, water-insoluble glass frit which,when.

now Patent Number. 2,697,159.

mixed with the other flux ingredients, the mixture ap- Grinding reducesthe 6 plied to the welding rod and the assembly heated, softens materialin water will serve this purpose. When the and wets both the other fluxingredients and the weldglass binder of the above-discussed copendingapplicaing electrode. Thus, when the assembly is cooled the tion isemployed, water may be incorporated in the discrete particles of fluxingredients are bonded to each mixture. The resulting wet mixture willbe in the form other and to the welding electrode by means of the low ofa plastic mass which may range from a stifi, doughmelting, hydrophobic,water-insoluble glass. In this like body suitable for application byextrusion under connection, a particularly advantageous glass for usepressure, to a thin, fluid slurry suitable for application as a fluxcoating binder is one having an analysis comby dipping, spraying,brushing, and the like. The coatprising oxides of at least two of thealkali metals seing composition may then be applied to a weldingeleclected from the group consisting of sodium, potassium, 1O trodefollowing conventional coating procedures.

lithium and rubidium in an amount between about 20 The present inventionis not concerned with the parmol percent and about 40 mol percent; atleast one of ticular electrode to which the coating is applied. The thedivalent metal oxides selected from the group conelectrode itself, as iswell known, may vary widely as to sisting of CaO, MgO, SrO, CdO, MnO,FeO, C00, and size, form, and composition. So far as size is con- NiO inan amount between about 5 mol percent and cerned, the present commercialelectrodes range from about mol percent, the total of said alkali metala wire of about inch in diameter up to a rod having and divalent metaloxides being between about 30 mol a diameter of about inch. Theelectrodes are generpercent and about 55 mol percent, and the mol ratioally cylindrical in form, and generally solid, although of said alkalimetal oxides to said divalent metal oxide hollow rods may be employed incertain instances. The being between about 2 to 1 and about 8 to 1; SiOzin an 20 metal from which the electrode is made depends upon amountbetween about 30 mol percent and about 60 various factors, including thetype of metal to be welded. mol percent, and TiOz in an amount betweenabout 2 Thus, when carbon steel is to be welded, the electrode molpercent and about mol percent. Preferably, the will also be of carbonsteel, that is, a steel containing glass also comprises fluorine up toan amount equivalent between about 0.1% and about 0.35% carbon. On toabout 20 mol percent of NazFa, B203 in an amount 25 the other hand,where alloys are to be welded, the elecup to about 40 mol percent and/ora trivalent oxide trode may be of such alloys. selected from the groupconsisting of FezOs and A1203 The preparation of the novel glass fritand of flux coatin an amount up to about 10 mol percent. ingcompositions comprising the frit of the present inven- In preparing theflux coating, the materials making tion will be more clearly understoodfrom a consideration up the coating will be in relatively fine particlesize. of the following specific examples which are given for the As iswell known, the exact particle size of the parpurpose of illustrationonly and are not intended to limit' ticular ingredients may varysomewhat depending upon the scope of the invention in any way.considerations known in the Welding art. Often it is The following tablesets forth the composition of redesired to employ a combination ofextremely fine mapresentative glass frits prepared in accordance withthe terial with somewhat coarser materials, and the particle presentinvention.

Potassium Titanate KzO.. 17-19. MnO 18506.-

a; up to 1%. ZrOz. 4. 6 u to 2 1 v 1 2.2 2.3 p

o 2. 7 2. 5 up to .47. s1 oi... 26.2 24. 7 29. 4 up to 1.5%; T102---27.6 25. 7 24. 0 44%. FezOa 4. 7 4. 3 4. 8 up to 3%. Al:O3 3. 6 3.1 3. 8up to 1.5%.

size distribution selected will present no problem to Exaniple XI oneskilled in the art. In general, the particle size of The com ositions ofthe resent invent'o a t the materials Wlll not be greater than about 40mesh. p p l n re ested for hygroscopicity and compared with potassiumtitanate While the fineness of the m te y be allything as follows: Asample of the frit of Example X of the below this figure, usually theaverage particle size thereabove Table and a sample of potassium tjta teof of will not be less than about 325 mesh. merce, each predried, arestored at 75% relative humid- The glass frit of the present invention ismerely mixed ity for 5 days. The weight gain was then measured with withthe other flux coating ingredients, and for this the following results.purpose any mixing device, such as a Z-bladed mixer Weight gain or edgerunner mill, may be employed. The proportion per cent of the glass fritof the present invention to the other PP X 2-33 flux ingredients in themixture may vary widely, de- Potassmm manate pending upon the presenceor absence of other potas- Since the particle size has an effect uponmoisture absium-containing compounds in the mixture and upon sorption,it is pointed out that the frit of Example X the amount ofarc-stabilization through the presence of as a tually fin r than thepotassium titanate employed. potassium-containing material desired inany particular The frit of Example X, y Sieve analysis, Was case Ingeneral, however, the glass frit of the present through a 325 meshwhereas the potassium titanate was invention will make up between about3% and about only 715% through, 10% of the other coating ingredientsFrom the foregoing it is seen that the composition of the invention isabout half as susceptible to moisture pickup as potassium titanate,although the frit of Example X contains 50% more K20 than does potassiumtitanate.

In applying the flux mixture to the electrode, a liquid is incorporatedin the mixture, the amount of liquid being sufficient to provide aplastic mass capable of being applied to the electrode. When a solublesilicate, gum, Example or the like, is employed as a binder, a solutionof such In making up a welding electrode coating the frit of 7 Example'X is' mixed with other flux" coating ingredients in-tlie' followingproportions:

Parts Highcarbon ferromanganese 4.0 Ferrotitanium 4.0 Ferrosilicon 4.0Calcium carbonate 23.0 calcined. alumina 13.0 Fluorspar 13.3 Rutile 12.3Clay 2.0. Sodiumalginate 1.0 Glass bond 15.0: Frit of Example X 8.4Water- 16.5

1L water-insoluble, nomhygroseepic frit having the follow ing analysis-zLig3.9%, K2O- .O%, New-14.9%,. MnO -1'.7'%', Alfie-8.4%, TiO 11.0 Ca04.9

SiOHl.I %..and F'-5.9% (reported separately), and fusible ata lowtemperature to bond the ingredients to each other and to the weldingrod.

The abovemixture isextruded? around a welding rod, and; the. assemblyis..heated to about 1175 F. for. 5 minutes to cause softening oftheglass bond,.then cooled.

When potassiumiitanate. which had been stored. for 6 months wassubstituted for the frit of Example X, in the foregoing formulation,.thematerialcould. not be-extruded. This isbelieved to be due to, a reactionbetween potassium hydroxide in the potassium. titanate (formed byreaction between potassium titanateandits own water of hygroscopicity)and the sodium. alginatev which. leads to chemical breakdown and loss offilm-formingproperties of the latter.

When the frit of Example X wasstored for 6' months and used in theforegoing formulation, extrusion was perfectly satisfactory.

Considerable modification is possible in the selection of the variousmaterials used in making up the glass frit of the invention and in theproportions thereof, as well as in.the.selection.of. the variousingredients usedin making up welding electrode coatings withoutdeparting from the scope of the present invention.

I claim:

1. A water-insoluble, hydrophobic composition in the formtofaglass fritconsisting essentially of'between about 20%" and about 33% of K20;between about 20% and" about140% of Ti02, and between about 17% andabout of'SiOz, the sum of the K20 and "H02. and Si02 7 making up betweenabout 75% andabout 94% of the glass; at least one of the divalent oxidesselected from the group consisting of CaO in an amount between about .5and about 10%,, MgO' in an amount. between about .1 and'about 8% andMnOin an amount between about .5 and about 15%, and at least one ofthetrivalent. oxides selected'from the group consistingof Fe203 in anamount between about .1 and about 15%, B203 in an amount between about.5 and. about 20%, and A1 03 in an amount between about .1 and about 8%,all percentages recited herein being on a weight basis.

2. A water-insoluble, hydrophobic composition in the form. of a glass.frit, consisting essentially of between about 24% and about29% of K20;between about 22% and about 33% of Ti02, and between. about 24%. andabout 32% of Si02, the sum of the K20 and Ti02 and Si02' making upbetween about 78% and about 90% of the glass; at least one of thedivalent oxides selected from the group consisting of CaO in an amountbetween about 1 and about 6%, MgO in an amount between about 1 and about3% and MnO in an amount between about 3 and about 10%, and at least oneof the trivalent oxides: selected from the group consisting of Fe O3 inan amount between about 4 and about 10%, B203 in' an amountbetween about1 and about 10% and A1203 in an amount between about 2 and about 5%, allpercentages recited herein being on a weight basis.

3. A flux-containing welding electrode coating comprising a mixture ofparticles of welding flux ingredients and of a water-insoluble,hydrophobic glass frit consisting essentially of between about 20% andabout 33% of K20; between about 20% and about 40% of Ti02', and betweenabout 17% and about 40% of' Si02, the sum of the K20 and TiOz and Si02making up between about and about 94% of the glass; at least one-of thedivalent oxides selected from the group consisting of Ca0 in an amountbetween about .5 and about 10%, MgO in an amount between about .1 andabout 8 and MnO in an amount between about .5 and about 15%, and atleast one of the trivalent oxides seelcted prising a mixture ofparticles of welding flux ingredients:

and of a water-insoluble, hydrophobic glass fritconsisting essentiallyof between about 24% and about 29% of K20; between about 22% and about33% of Ti02, and between about 24% and about 32% of Si02, the sum of theK20 and Ti02 and Si02 making up between about 78% and about of theglass; at least one of the divalent oxides selected from the groupconsisting of CaO in an amount between about 1 and about 6%, MgO in anamount between about 1 and about 3% and Mn0 in an amount between about 3and about 10%, and at least one of the trivalent oxides selected fromthe group consisting of Fe203 in an amount between about 4 and about10%, B203 in an amount between about 1 and about 10% and Al203 in anamount between about 2 and about 5%, all percentages recited hereinbeing on a weight basis.

References Cited in the file of this patent UNITED STATES PATENTS1,909,217 Notvest May 16, 1933 1,925,560 Kinzie et a1 Sept. 5, 19332,344,621 Lemmerman Mar. 21, 1944 2,590,893 Sanborn Apr. 1, 19522,660,531 Fraser et al .Nov. 24,1953.

1. A WATER-INSOLUBLE, HYDROPHOBIC COMPOSITION IN THE FORM OF A GLASSFRIT CONSISTING ESSENTIALLY OF BETWEEN ABOUT 20% AND ABOUT 33% OF K2O;BETWEEN ABOUT 20% AND ABOUT 40% OF TIO2, AND BETWEEN ABOUT 20% AND 40%OF SIO2, THE SUM OF THE K2O AND TIO2 AND SIO2 MAKING UP BETWEEN ABOUT75% AND ABOUT 94% OF THE GLASS; AT LEAST ONE OF THE DIVALENT OXIDESSELECTED FROM THE GROUP CONSISTING OF CAO IN AN AMOUNT BETWEEN ABOUT .5AND ABOUT 10%, MGO IN AN AMOUNT BETWEEN ABOUT .1 AND ABOUT 8% AND MNO INAN AMOUNT BETWEEN ABOUT .5 AND ABOUT 15%, AND AT LEAST ONE OF THETRIVALENT OXIDES SELECTED FROM THE GROUP CONSISTING OF FE2O3 IN ANAMOUNT BETWEEN ABOUT .1 AND ABOUT 15%, B2O3 IN AN AMOUNT BETWEEN ABOUT.5 AND ABOUT 20%, AND AL2O3 IN AN AMOUNT BETWEEN ABOUT .1 AND ABOUT 8%,ALL PERCENTAGES RECITED HEREIN BEING ON A WEIGHT BASIS.